Oscillating system



Dec., 3, g

G. H. SCHIEFERSTEHN OSCILLATING SYSTEM HEER??? Filed Nov. 6, 1924, '2sheets-sheet 1 Fig Figl.

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menta! Dec. 3, 1929 UNITED STATES PATENT oFFIcE oscuLA'rING SYSTEMApplication led November 6, 1924, Serial No.

My invention relates to improvements in oscillating systems.

In rotating mechanisms intended for the transmission of energy or toperform work 5 the. number of revolutions are as a rule so regulatedthat the best effect is obtained for the'particular work to be done.Thus for example a circular saw will be driven at a speed at which thesawing operation produces the most favorable effect whilstsimultaneously still keeping the heat generated within permissiblelimits. However, in the case of mechanisms which are moved to and fro,the speed varies four times from zero to a max- 15 imum during eachperiod. If the periodicity of such a'device' is so selected that themost favorable speed lies between zero and the maximum speed attained,then it must be passed four times during each period for a very shortinterval of time.

For a better understanding the invention will hereinafter be more fullyex lained with reference to the accompanying rawings.

Fig. 1 shows the velocity and tension curves of an oscillation occurringin accordance with the sine law; Fig. 2 shows diagrammatically astructure capable of oscillations, in which, according to the presentinvention, in the state of oscillation, the velocity and tension curvesare not in accordance with the sine law, but are latter; Fig. 3 showsthe velocity and tension curves of a device in laccordance with thepresent invention; Fig. 4 shows diagrammatically a structure capable ofoscillation in accordance with the present invention, in which anotherform of elastic means and another kind of coupling for starting thescillations are used; Fig. 5 shows diagrammatically a structure capableof oscillation in accordance with the present invention, in which, afurther manner of coupling is used; Figs. 6 to 11 show other possiblemanners of coupling for starting structures capable of oscillations inaccordance with the present invention; Figs. 12 to 15 and 17 showelastic means for obtaining the object of the present invention; Fig. 16shows so-called elastic lines, i. e. the shape of the bending of elasticmeans for various dimensions; Fig. 18 shows systems the oscillations areusually in accord- 748,028, and in Germany November 15,-1923.

by way of example an embodiment according to the present invention.

During the to and fro motion of a mechanical device, driven by acrank-loop which moves according to the sine law as-shown in 5 Fig. 1 ofthe accompanying drawings, themost favorable working speed, which maycorrespond to the ordinates y and y', would intersect the curve at thepoints AB and CD.

A practically identical process occurs in the case of a crank gearing,which (with an endless connecting rod) also moves in asine curve.

These considerations show that numerous mechanisms which arecompelled toreciprocate for the. purpose of transmitting power actJ veryineficiently as regards theutilization of the most favorable speed.

However, also in the case of oscillating ance with thel sine law andthis moreover forms the basis of the entire study'of oscillations.

The present invention is based on a new perception according to which itis possible to construct elastic oscillating mechanical systems-providedthat they are loosely coupled together-in such a manner that the courseof the speed and tension curve will differ entirely from the sine curve.Both curves may in the median position of the os'- cillating systemundergo such a strong 'deformation i. e., lattening, that the speed willbe maintained approximately constant during a considerable period andmay thus be adapted to the most favorable working speed. Such a systemtends after each change in direction to return to the most favorablespeed as rapidly as possible and maintains this speed approximatelyuntil shortly before the next sudden change in direction.

Fig. 2 shows diagrammatically by way of example a construction suitablefor carrying the invention into practical etfect. a is a mass which isjointed to the top of springs b at the point c by means of twoconnecting rods u. The springs b are fixed at their base at points lm..Two pairs of springs b', b and b2 b2 are also fastened at m. A lever 'vis jointed to the mass a and is adapted tobe moved to and fro by meansof a crank g convlacted thereto, thus tensioning the two couplingsprings k 7c. When the crank g is rotated only a very small part of thismovement will be transferred to the mass a, whilst the coupling springs7c 7c will be strongly tensioned. On continued rotation of the crank,the oscillation of the mass a will always increase and it Will thus bendthe springs b b more and more, so that they thereu on touch and bend thesprings b', b and nally the springs b2, b2. By the introduction of thepairs of springs b and b2 the elastic means will be very greatlyincreased at this moment and the speed and tension curves which areflatter in their middle position will now ascend and descend withrelative suddenness and thus the course of the curve shown in Fig. 3which is that desired in accordance with the present invention, isobtained.

Assuming that the oscillating system is in one of its extreme limitpositions, then its speed at this point is zero. In the next moment, onleaving this point the speed of the mass a increases relatively quicklyas shown by curve I, Fig. 3, attaining the most favorable working speedatl the point A, from which the speed curve is only slightly deflected.Only on reaching the point- B (Fig. 3), does the speed curve sink belowthe most favorable working speed B and then falls rapidly to zero afterwhich the same process of movement occurs in the reverse direction,passing the points CD as illustrated by the negative part of the curve.The potential curve II, Fig. 3, which illustrates the spring-tension,runs lduring its first quarter as a reflected image of the speed curveI. It starts from the median position, and rises quickly to its maximumat the point E after insertion of the springs b', b and b2, b2. From Eonwards the potential curve sinks as rapidly and as symmetricallytowards the'next median position, l' rom whence it begins to assume anegative form retaining the same external shape. As previously stated itis evident that since the system commences with small movements and onlygradually describes larger oscillations, the energy transmitted by thecrank g must be conveyed through a flexible medium, i. e. a so-calledloose coupling, because each arbitrary connection would prevent the massa oscillating freely with a variable amplitude.

The term loose coupling is used to designate a means or a method fortransmitting energy in a mechanically oscillating manner by yieldingmeans, e. g. elastic means, such as springs, gasor air-cushions etc.,inert masses, such as a fly-wheel, reciprocating masses, nonbalances,pendulums, etc., friction, liquidor other resisting or varying means, ora combination of two or more of such means, in which two oscillatingmechanical systems as regards amplitude and periodiclty are made soalike and are so connected by yielding mechanical means that the ratioof the energy transmitted by the coupling to the energyexisting in theoscillating structure during operation Am is equal or substantiallyequal to the double dampening decrease ='28 of the oscillatingstructure, i. e.

or in other words, that a'yielding mechanical member (which isdesignated as the loose coupling), which acts between-a driving and asubstantially equally tuned driven oscillating mechanism transmits foreach half oscillation an energy which, as regards size, shape and phase,compensates the loss during each half oscillation. The loose couplingtherefore, isl adapted to transmit energy, during a corresponding phasedisplacement, by mass action, tension,'friction or by way of a fixedconnection during a certain period of time without disturbing theoscillation.

Couplings can be, divided into elastic couplings, mass couplings,friction couplings and time couplings. Each of these four differenttypes of couplings have a potential form as 'shown in Figs. 4, 5, 6 and?and a kinetic form as shown in Figs. 8, 9, 10 and 11, so that eightdistinctly different rudimentary forms are possible. o

These eight rudimentary forms can be combined together in various ways;thus for instance, in any practical embodiment the potential or thekinetic element may preponderate as desired.

Moreover, it is conceivable that mass and elasticity or any othercombinations are applicable simultaneously, and that finally three, fouror more coupling properties may reside within one and the same couplingconstruction. Any one of these constructions characterised as loosecouplings or any combinations of such means suitable for such couplingsmust however be used in combination with the herein-describedoscillating system in order to produce the above described effect, i.e., flattened oscillation.

In Fig. 4 relatively large power is transmitted over a small path by aneccentric gear g through a connecting rod lk to the lever c, whichrepresents the coupling, and energy is conveyed in a potential form tothe spring b and transferred to the oscillatable system consisting ofthe mass a and the springs b. As soon as the speed of the eccentric gcoincides with the natural frequency of the oscillating system a b', sothat two systems are in tune, more or less energy is transmitted to theoscillating device according to whether the coupling is a. tighter orlooser one. The coupling may be made tighter or looser by moving theconnecting rod it in relation to the coupling lever c, that is byshortening or lengthening the lever arm. v

Fig. 5` illustrates a device in which the energy is transmitted in theabove-described manner by the eccentric g and rod h to the lever c andfrom thence to the oscillating System consisting of the mass a andsprings b. In this case again the maximum of energy transmission isobtained when resonance takes place.

In the device shown in Figs. 6 and 6a power is transmitted by frictionbetween the lever k and the point of attachment of the mass a the actionof the eccentric g and connecting rod L being the same as thatpreviously described. p

In Fig. 7 the eccentric g and rod are connected to a lever k. A ratchetc which is fastened to the lever c only transmits energy to the mass awhen the speed is less than that of the lever c. Thus, thecoupling devvice of Fig. 7 only comes into operation at certain periods and maytherefore be designated as a time coupling. p

In Fig. 8 the transmission to thel elastic coupling is effected by thecrank' g through the connecting rod h. The power, which in this case istransmitted through a larger crank path, is essentlally smaller so thatunder otherwise similar conditions the same energy can be transmitted tothe oscillating system. Thus whilst the transmission in the case of thecouplings shown in Figs. 4 to 7 is effected potentially the transmissionin the case of the couplings illustrated in Figs. 8 to 11 is effectedkinetically.

Fig. 9 illustrates a kinetic mass-coupling. The crank gear g k drives areciprocating lever 7c which is provided with an adjustable mass G. Theinertia of this mass causes the mass a to oscillate.

Fig. 10 shows a kinetic friction coupling.

In this case the crank gear g k drives a fricf tion lever c whichtransfers the power to the mass.

Fig. 11 represents a kinetic time-coupling, the crank gear g L drivesthe lever la, to which is attached a ratchet e which periodicallytransfers energy to the mass a. According to choice and dimensions ofthe individual springs and\ the supplementary springs b', b and b2, b?it is possible, .as canbe easily understood to make the speedcurve moreor less flat. The same result is obtained when. springs are used inaccordance with Figs. 12,13, 14 and 15.

Fig. 12 illustrates a double bufi'er spring the end coils of which areof smaller'dimensions. The springs are compressed or extended betweentwo flanges f. On moving the two flanges towards each other naturally cthe weaker coils I and II are compressed in the first place, and sincethey gradually recede into the coils II and III and thereupon IV theyare finally cut out.

A similar result is obtained when using a sprino' dimensioned as show nin Figs. 14.- Or 15. luch a spring which is greatly ovcrdimensioned inthe vicinity of its point of attachment bends at first mainly at itsupper part until the bending strain of the upper part is graduallytransformed into a tension, when the lower part will be more stronglyloaded and will be able-at a relatively small amplitude-to accumulate arelativelyv large amount of potential energy.

` Fig. 17 showsdiagrammatically by way of example another constructionsuitable for carrying out the invention. In this case a flat spring b isused of equal breadth and strength having suitable slit so that itbecomes a body ot equal strength or an overdimensioned spring.

In the embodiment shown in Fig. 18, two sets of elastic means b2, b1, b,b1, b2, are firmly clamped on a base plate e by means of a clampingdevice m. These elastic means, at their bases,are made broader andstronger, and are provided with openings d. By each of the said meansthe result is obtained that the elastic line, i. e. the shape `assumeddurling the bending follows the curve III, accordaccording to thepresent invention, is caused to oscillate by a loose coupling k. To thisend, the driving power is transmitted to the oscillating structure bymeans lof a crank mechanism g, L, andthe coupling member lf: from ashaft Z which is supported in the bearing f. The crank rod l1. isadjustable at the coupling member, so that by a modification of theadjustment, thepower transmitted to the oscillating structure can bevaried.

It is possible to conceive that the desired result may be obtained withother spring constructions than herein described without departing fromthe 'spirit ard scope of the invention. All springs attached at one endshow by their elastic lines, that is, the curve obtained by holding oneend firmly and bending the other, whether or not they are suitable forthe purposes of the present invention. Springs in which the elastic lineruns similarly to the curve I of Fig. 16, are unsuitable whilst a springof triangular form bending through a circular arc as shown by the curveII of Fig. 16 p gives a better result,

Y. spondingly decreased.

However this result can be considerably increased by springs, which areover-dimensioned at their point of attachment and which bend inaccordance with the curve III of Fig. 16.

Besides having the aforesaid advantage of better adapting theoscillation curve to the most favorable working speed, this device alsorenders possible the employment of greater amplitudes of oscillation atrelatively high speeds. It is evident that a relatively large mass canonly be moved to and fro at high speeds by springs bending in accordancewith curve I (Fig. 16) when these springs are strongly dimensionedthroughout. In the case o springs which as above described, in theirmiddle position when relatively strongly bent take up comparativelysmall power, but on the other hand are adapted to accumulate largequantities of potential energy in their extreme end-positions it ispossible to obtain a high periodicity through a relatively large pathand with a large mass, i. e., springs of this type combine theadvantages of great elasticity and capability of accumulating energy.

The desired result, that is oscillating systems with relatively flatspeed and tension curves in the medium positions and steep ascendingcurves in the extreme end positions may also be obtained by theemployment of gasand air cushions in combination with loose couplings.

An interesting property of the hereinbefore described systems is that atsmall amplitudes they exhibit a slow natural frequency whilst atincreasing amplitudes their natural frequency always increases. Thus, ifa system is moved to and fro through a very small amplitude thesupplementary springs may be regarded as being quasi cut out, wherebythe natural frequency of the system is corre- In this form the wholesystem would approach the resonance condition at a krelatively lownatural frequency. However before it can attain resonance, thesupplementary springs are cut-in owing to the increasing amplitude ofoscillation and thus the natural frequency is increased, this procedureoccurring several times according to the number of the supplementaryelastic means used. Thus such a system-starting from a low periodicity,up to its highest natural frequencyis always in a condition immediatelybefore that of resonance, and therefore always gives an excellenteiiiciency. Systems of this kind should therefore be regarded asparticularly elastic, because they have an excellent efficiency withinwide limits.

When the maximum speed and thus the maximum power transmission isattained a low variation in the load also produces only, aslightvarition in amplitude, because at the last moment only small tensions ofthe oversimultaneously.

' The employment of the aforesaid systems in working machines such assawing machines, mowing machines and the like offers special advantages,as the most favorablel speed is maintained for a relatively long time.

A further important advantage of the aforesaid systems is that theover-dimensioned springs fitted for large energy accumulation do notslacken and are not destroyed even with oscillations of highperiodicity.

It is obvious that the springs of the hereinbefore described type arevery suitable for use as coupling springs, just because these springsallow a large energy transmission when greatly bent. Theover-dimensioning of the springs is especially favorable because theirlife is prolonged in spite of the high periodicity and the heavy strain.

The distance between the several spring laminations may be greater orsmaller and the individual laminations may be provided at their free endwith rollers or balls in order to diminish damping effects.

I do not claim broadly herein the method of and means for loosemechanical coupling nor the other features not specifically pointed outin the claims, having made a separate application for such featuresunder Serial No. 688,876 filed J anuary 26, i924.

Claims: 4

1. An oscillating mechanical system comprising a mass., and elasticmeans operatively connected with said mass and having a resistanceincreasing more rapidly than lineal' as to deflection unit, theconnection of said mass with said elastic meansconstiuting apseudo-harmonic oscillating structure, a mechanism for reciprocatingsaid structure, and a yielding device operatively connecting saidstructure and said mechanism and adapted to transmit for each periodonly so much energy that the ratio of the energy thus transmitted to theenergy existing in said oscillating structure equals or substantiallyequals the double vdampening decrease of said oscillating structure.

2. An oscillating mechanical system comprising, in combination, areciprocating mass, a plurality of elastic members symmetricallyarranged in stages to successively apply resistance to movement of saidmass, thereby accumulating energy, said members giving up energy to saidmass on change of direction of movement, a mechanism for reciprocatingsaid massand a loose coupling between said mass and said mechanism.

and said mechanism.

4. An oscillating mechanical system comprising, in combination, areciprocating mass, a plurality of double curved springs with two pointattachment at each end of said.

ratio of the energy thus transmitted to the energy existing in theoscillating unit equals or substantiall equals the double dampeningdecrease o said oscillating unit.

- In testimony whereof I aix my signature.

GEORG HEINRICH SCHIEFERSTEIN.

mass, of which the movable end of one spring at each end of said mass isattached to the mass, and the remainder are adapted to act on said massin succession as the mass reciprocates, a mechanism for reciprocatingsaid mass, and a loose coupling between said mass and said mechanism.

5. An. oscillating mechanical system com pri-sing, 1n combination, areclprocating mass,

a set of springs arranged at each end of said mass, each set including acentral spring attached to said mass ,and one or more springs to eachside of said central spring and adapted to contact said central springupon displacement of said mass and adding resistance to movement of saidmass upon contact, a mechanism adapted to reciprocate said mass at arate corresponding to the natural frequency of vibration of the mass andelastic means, and a loose coupling between said mass and saidmechanism.

6. An oscillating mechanical system comprising, in combination, anaturally oscillating unit consistin of a movable mass, and a pluralityof e astic elements having stationary base points and movable headpoints, the cross section at the base points being greaterthan at thehead oints, a mechanism for reciprocating sai mass, and a yieldingmechanical means operatively connecting said mass and said mechanism andadapted to transmit for each period only so much ener that the ratio ofthe energy thus transmitted to the energy existing in the oscillatinunit equals or substantially equals the dou le dampening decrease ofsaid oscillating* unit.

7 An oscillating mechanical system comprising, inv combination, anaturally oscillating unit consisting of a movable mass, and a pluralityof elastic elements comprising slitted members having stationary basepoints and movable head points, the cross section at the base pointsbeing greater than at the head points, a mechanism for reciprocatingsaid mass, and a yielding mechanical means operatively connecting saidmass and said mechanism and adapted to transmit for each period only somuch energy that the

